Modern brake control systems monitor rotation of one or more wheels and modify a braking force applied to the wheel or brakes as necessary for proper braking. Such brake control systems are in widespread use in commercial and military aircraft, as well as in ground transportation vehicles. In use, these systems provide improved braking control, anti-skid and reduced stopping distances.
One of the central elements of such brake control systems is the wheel speed sensor or transducer, which provides data regarding the instantaneous wheel speed of the various wheels of the vehicle. An accurate measure of wheel speed is an important first step in detecting and then controlling braking conditions. Known wheel speed transducers convert a rotational speed of the associated wheel to electrical signals, and these signals then are employed by brake control circuitry, such as anti-skid control circuitry and/or automatic brake control circuitry, to control braking activity of the vehicle.
Conventional systems for monitoring wheel speed employ analog and/or digital sensors, wherein, for example, the wheel speed sensor produces a signal having a voltage or frequency that is proportional to the rotational speed of the wheel. The signal is transmitted from the sensor at each wheel to respective sensing and control circuits, which, for example, control the braking pressure to prevent skidding of the respective wheels.
If one or more wheel speed sensors fail or otherwise malfunction, anti-skid braking functionality may be lost. As will be appreciated, if such functionality is lost while the aircraft is on the ground, then the aircraft may not be authorized to fly, which can lead to flight delays. If such functionality is lost after the aircraft has become airborne, however, then aircraft braking may not be optimum.